(1) Field of the Invention
The present invention relates to electric motors that typically have an external motor component and an enclosure mounted adjacent an exterior surface of the motor for holding the component therein. More specifically, the invention pertains to the construction of an end shield for the electric motor where the end shield is provided with an integrally formed component compartment that protects the motor component from inadvertent contact and damage to prevent malfunction of the electric motor.
(2) Description of the Related Art
Electric motors to which the present invention pertains are common in the art. Typically, these types of motors are used in domestic appliances such as air-conditioning and refrigeration units for driving compressors and pumps that have high starting torque requirements. Generally, these single-phase induction motors have a hollow, cylindrically shaped stator with axial opposite end surfaces, and a rotor and shaft rotatably disposed within the hollow interior bore of the stator. The stator has windings wound axially through the stator bore, and end-turns from the stator windings are positioned adjacent the stator end surfaces. End shields are mounted to the stator end surfaces to form a portion of the exterior surface of the motor. The end shields protect the stator windings and end turns from inadvertent contact and grounding while providing a mounting surface for rotor bearings and shaft bushings. The end shields also prevent debris from entering the hollow interior of the stator and interfering with operation of the motor.
Typically, motors used in these high starting torque applications have stator windings that include both run windings for producing the rotating electrical field in the stator and auxiliary windings for starting the motor. For a capacitor start induction motor, a capacitor is permanently connected in series with the auxiliary windings to generate an electrical field phase shift in the stator between the run and auxiliary windings to begin rotation of the motor with the necessary starting torque. As the motor comes up to speed, the auxiliary windings are switched off line.
Generally, the capacitor used in these applications is relatively large in size such that it must be located external to the motor. The capacitor is typically positioned inside an electrical enclosure mounted on an exterior surface of the motor housing between the end shields. During manufacture of the motor, the capacitor is connected to the motor auxiliary windings and positioned on the motor exterior surface. The electrical enclosure is then placed over the capacitor and attached to the motor exterior surface by any of several methods, including welding, mechanical fasteners, through a system of complementing tabs and slots on the electrical enclosure and the motor exterior surface, or any combination thereof.
This method of housing and protecting the capacitor has many drawbacks. First, as stated previously, the methods of attaching the electrical enclosure to the motor exterior surface complicate assembly and are often inefficient. The electrical enclosure is a separate part that must be provided on the manufacturing lines and installed on the motor in a time consuming assembly operation that is inherently inefficient and costly. Additionally, when the motor component is installed in the electrical enclosure, the capacitor sometimes moves within the electrical enclosure. This movement within the enclosure often results in accidental grounding of the auxiliary windings or physical damage to the capacitor as it impacts with the interior of the enclosure. The likelihood of these occurrences increases when the motor is moved through the production lines and when it is installed in the appliance.
What is needed is an electric motor with an electrical enclosure that is formed integrally with a part of the electric motor so as to reduce parts and eliminate assembly operations during manufacture of the motor. Such an enclosure would hold the capacitor or other motor component away from the structure of the motor to prevent grounding of the capacitor or other component and malfunctioning of the motor. Such an electrical enclosure would protect the motor component from damage. Such an electrical enclosure would provide the electric motor with a low profile so as to reduce overall space considerations for the electric motor when it is installed in an appliance.
The electric motor of the present invention is provided with a component compartment integrally formed on an end shield of the electric motor. The component compartment houses and protects a motor component used for controlling the operation of the motor. The component compartment holds the motor component away from the structure of the electric motor to prevent the motor component from moving within the compartment. The component compartment prevents the component from being damaged, potentially grounding, and contributing to the malfunction of the motor from such movement. The component compartment has sufficient strength to protect the motor component from damage from impact with objects external to the motor.
The component compartment preferably extends axially away from the end shield so that the component compartment is positioned adjacent an exterior surface of the electric motor. This provides a low profile for the electric motor to reduce size considerations for the motor as it is used in the appliance. By forming the component compartment integrally with the end shield, the number of parts and number of assembly operations may be reduced, thus lowering the costs associated with the manufacture of the motor.